Nate used an ordinary car primer you get from Supercheap Auto. There are two versions. One being a primer (think this was grey) and the other paying a spray putty (think this was blue) which comes out a bit thicker and you sand it back afterwards (I think Septone was the manufacturer).

Happy to answer on his behalf. Precision is all through templates and ensuring pieces are cut to size accurately. The button from memory is a decal that he has applied to the face, while the screen is a decal placed beneath the cutout.

Due to the requirements of the course, we need to make a visual representation of the design. Our models are supposed to resemble the design with some level of accuracy, but on a model like this, an extra mm or 2 in width, thickness etc... is not going to be detrimental in communicating the product to the examiners.

This wouldn't be the best method in producing 10 to 20 sets, you would be looking more at rapid prototyping for the front cover or something similar in order to provide a consistent level of accuracy.